There are many applications in which it is desirable to concentrate the power from a laser array such as an array of many semiconductor laser diodes. One example is that of optical pumping of another laser such as an Nd:YAG laser. Another field is that of medical lasers. For example, lasers have been used to successfully treat vascular lesions through the method of selective photothermalysis. In surgical applications, a laser such as a 100 watt YAG laser may be desirable. 100 watt diode arrays are now available, but the difficulties in optically coupling the power from hundreds of diodes into a single fiber of a delivery system have limited commercial fiber coupled systems to 25 watts.
Geometric optics used to combine the outputs of multiple lasers are large, cumbersome and expensive. Another approach has been to couple the outputs from segments of a diode array into multiple fibers and dense-pack the fibers into a random bundle. Such a system is limited to about 10 watts and is expensive.
Yet another approach to combining the outputs of a laser array has recently been presented by Leger and Goltsos in "Geometrical Transformation of Linear Diode-Laser Arrays for Longitudinal Pumping of Solid-State Lasers," IEEE J. Quantum Electron., Volume 28, pages 1088-1100 (1992). In that system, a diffractive optics transformer transforms the beams from a linear array of many semiconductor laser diodes into a two-dimensional array of collimated beams which may then be focused to the end of an optically pumped laser.